1. Field of the Invention
The present invention relates a vehicle brake device including: a fluid pressure booster which includes a control piston having a front end wall formed at its front end and formed in a bottomed cylindrical shape, and which adjusts and applies a fluid pressure of a fluid pressure generating source to a boosting fluid pressure chamber in accordance with the operation of the control piston in the axial direction so that a reaction force based on a fluid pressure of the boosting fluid pressure chamber is equal to a brake operation input from a brake operation member; and a stroke simulator which includes: a simulator piston fluid-tightly and slidably connected to the rear portion of the control piston while forming a stroke fluid chamber for introducing an operation fluid thereinto in a gap with respect to the front end wall, and connected to the brake operation member; a guide shaft coaxially disposed inside the control piston while allowing its front end to come into contact with the front end wall or a slide member accommodated in the stroke fluid chamber to be connected to the front end wall and allowing its rear end to be relatively slidably supported to the simulator piston; and an elastic body surrounding the guide shaft while being interposed between the front end wall or the slide member and the simulator piston, and accommodated in the stroke fluid chamber, and which is provided between the control piston and the brake operation member so as to stop a forward movement of the simulator piston relative to the control piston by sealing the operation fluid inside the stroke fluid chamber in a forward stroke not less than a predetermined stroke of the control piston, wherein a master cylinder is operated in accordance with the fluid pressure of the boosting fluid pressure chamber.
2. Description of the Related Art
JP-A-2006-282012 discloses a vehicle brake device having a structure in which a stroke simulator including an elastic body interposed between a control piston and an input piston connected to a brake operation member, a guide shaft passing through the elastic body, and the like is provided between the brake operation member and the control piston of a fluid pressure booster, and a relative forward movement of the input piston with respect to the control piston is stopped by sealing an operation fluid introduced into the control piston inside the control piston during a forward stroke not less than a predetermined stroke of the control piston.
However, although the elastic body is allowed to have hysteresis involved with a brake operation stroke and a brake operation input while being deformed in response to a brake operation of the brake operation member to be brought into contact with the inner surface of the control piston, a predetermined hysteresis is not obtained when the operation fluid is locked between the control piston and the elastic body due to the deformation of the elastic body before the forward stroke of the control piston reaches a predetermined stroke. For this reason, in the vehicle brake device disclosed in JP-A-2006-282012, a circulation path used for permitting the circulation of the operation fluid is provided in the guide shaft and the slide member coming into contact with the front end of the guide shaft and connected to the front end wall of the control piston so as to prevent the operation fluid from being locked between the control piston and the elastic body before the forward stroke of the control piston reaches a predetermined stroke. Accordingly, in such a structure, since the circulation path is formed in the guide shaft and the slide member, a perforating needs to be performed thereon. As a result, the processing cost is increased, and the structure is complex.